There were 144 orbital rocket launch attempts in 2021, which is a record — and the numbers are just going to keep going up from here. Everyone seems to want to go to space. Demand is higher than ever. That’s why the industry is taking note of the environmental impacts of rocket fuel — and looking for more sustainable fuels and alternatives.
Biofuels are of huge interest to the rocketry industry because they’re more sustainable and less harmful to the environment than current options. One promising option from Lawrence Berkeley National Lab promises more energy density than any current fuel option available — without the toxic byproducts of petroleum. How would this biofuel work, and what are the downsides and challenges? Here’s what we know.
Bacteria as Sustainable Biofuel
This new fuel, called POP-FAME (polycyclopropanated fatty acid methyl ester), is based on the antifungal bacteria Streptomyces. Project leader Jay Keasling specifically focused in on this molecule because of its shape, but Streptomyces has proven difficult to grow in a lab. However, because it had been genetically mapped, the team attempted to recreate the bacteria’s shape without copying the more troublesome parts of the structure — which would make it easy to replicate. They succeeded, and POP-FAME is the result.
The key to this new potential biofuel is in its shape: It has three carbon rings in the shape of a triangle. Typical fuels also have carbon chains — but they aren’t subject to the same stress that a sharper 60-degree angle creates. Energy is created when these bonds are broken, and these bonds under duress (at a sharper angle) produce a lot more energy when broken than typical fuels do. What’s more, because of its shape, it can be packed even tighter than regular petroleum, which further increases its energy potential.
The potential energy output of POP-FAME is enormous. According to the Science News release, it will be “more than 50 megajoules per liter after chemical processing.” In comparison, a popular kerosene-based rocket fuel has around 35. Basically, this means that it has the potential to be more energy efficient at a lower consumption rate — and because it’s biofuel, it will produce fewer toxic byproducts.
How Could Biofuels Change the Aerospace Industry?
The force of Earth’s gravity is significant; as a result, it takes a lot of fuel to propel a rocket out of Earth’s atmosphere. When there were just a few rocket launches a year, no one paid much attention to environmental costs. But now that rocket launches are happening more regularly, experts are taking notice.
While it’s too early to say that this biofuel would have no effect on climate change or be completely neutral (even simple, seemingly harmless byproducts such as water can have an effect on climate change, after all), it will likely produce lower toxicity than current options.
Additionally, it’s important to take note of energy efficiency and costs. Inexpensive, sustainable fuels would bring the costs of reaching orbit down, which would encourage more launches. That, in turn, might spur a new era of space exploration and travel. What’s more, sustainable biofuel that’s easy to produce could make Mars trips feasible — once astronauts arrive, they could simply grow the fuel needed to get them back home.
What Are the Next Steps?
It’s important to note that POP-FAME is still in the very early stages. The team hasn’t even done field tests yet, so all of this is still theoretical. Still, POP-FAME has performed excellently in simulations. These tests have shown that the molecule is safe and stable at room temperature. In contrast, liquid oxygen and liquid hydrogen, two popular rocket fuels, must be kept at -297 degrees Fahrenheit and -423 degrees Fahrenheit, respectively.
Now the challenge is to produce enough of the biofuel for testing, which could take a while. Additionally, scientists want to test out different applications of biofuels for jet fuel and other possible uses. In other words, it will be a long time before this biofuel is ready for any practical uses — but it’s incredibly promising for right now.
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